The present invention relates to a camera system for monitoring a space area, and in particular to a camera system for safeguarding an automated installation arranged in such a space area.
In many industrial and non-industrial applications, movement sequences and/or production processes are carried out in an automated fashion. As a general problem, the automated sequence can constitute a danger to persons or objects present in the region of the automated installation. For safeguarding purposes, use is typically made of light barriers, light grids, laser scanners, safety gates and guard doors. These elements serve the purpose of blocking off the space area around the automated installation. As soon as a light barrier or a light grid is penetrated, or a guard door is opened, the dangerous movement of the automated installation is stopped, or the installation is brought into a safe state in some other way.
However, light barriers, light grids, guard doors and safety gates are limited in their flexibility and require a comparatively high outlay on mounting and installation. Laser scanners are somewhat more flexible, but still remain limited in their ability to distinguish between dangerous and safe situations.
Attempts have therefore been made for some years to employ camera systems in order to safeguard automated installations that are a source of danger. DE 199 38 639 A1, for example, discloses such a device, although the camera still operates in a way similar to a light barrier or a light grid in this case because it monitors a known linear pattern arranged in front of the installation. Recent approaches such as disclosed by EP 1 543 270 B1, for example, attempt to use the camera system to record a three dimensional image of the space area including the monitored installation. Virtual safety gates can then be defined around the installation in a flexible manner by means of a suitable image evaluation.
However, such approaches place high requirements on the resolution and accuracy of the three dimensional image recording. Moreover, the intrinsic safety of the camera system must be ensured, that is to say the safety function may not fail even under unfavorable operating conditions and/or in the event of functional failures of the camera system.
DE 10 2004 020 998 A1 discloses a prior art device and, in particular, a preferred imaging optics for a safety-related camera system. However, this reference does not provide any proposals for a stable and reliable mechanical design of such a camera system, which design ensures the required functional reliability and, moreover, enables cost effective mounting.
Mechanical concepts for the design of cameras are, of course, to be found in other fields of application. For example, reference may be made to US 2003/0025826 A1 and to JP 2000-089 122. These publications contain proposals for the mechanical design of miniaturized cameras such as are used for applications in mobile telephones, personal computers, in motor vehicles or as door spies. However, these camera systems are neither capable, nor envisaged for the purpose, of recording a three dimensional image of a space area in order to safeguard a dangerous installation as a function thereof. In particular, these publications do not contain any proposals for integrating a number of cameras in a cost effective way and with a very high degree of accuracy to form a stereo camera system. In a stereo camera system, two or more cameras are used for generating a three dimensional image of the space area by means of stereo image evaluation. This requires the at least two cameras to be positioned very exactly relative to one another.